Permanent magnet synchronous motors of relatively light weight, small size, simple structure, and high power density have played an important role in, e.g., industrial and agricultural production, as well as other applications. With the development of permanent magnetic materials and power electronic devices, permanent magnet synchronous motors are becoming more widely used. For some applications, the system cost may be controlled to a maximum extent, so position “sensorless” techniques may be applied in order to reduce system costs because a normal position sensor (e.g., photoelectric coded disk, rotatable transformer, etc,) may be avoided. In some cases, vector control can be used in a position sensorless permanent magnet synchronous motor; however, such an approach may need an advanced processor in order to process the relatively complicated algorithm and heavy computational load.